Dad
The monsters were fine, you taught me how to handle monsters, you both did.
Honestly I'm surprised that you've managed to keep it from him this long, when I'm from you two can hardly keep anything from each other, but that might be because when I'm from you've known each other nearly twenty years.
But yes, he needs to know, and I still say it's better if you tell him before I show up. Don't let him drink beforehand though, afterwards, sure, he'll probably need it, but not beforehand. Just let me know when I should come by.